Hi Andy,

re:
> Another one - I think my surface is too complex for MoI to work with easily. I can't
> extrude it. I've tried two ways to get it into MoI - use the obj to 3DM converter and
> the obj import in V4.

The problem is you don't have a CAD surface, it looks like you have polygon mesh data in the form of triangles.

The OBJ import in MoI V4 is for converting a sub-d control cage into a CAD surface, your mesh looks like it is not configured as a sub-d control cage where it should be a sparse control cage made up of quad polygons.

MoI and other CAD programs in general are not designed to work on this kind of dense triangulated data.

You will probably need to use a polygon mesh editing program to work on this type of data, not a CAD program. I'd recommend trying 3D Coat or ZBrush to start with.

To work with it in CAD you would probably need to go through a process called "reverse engineering" that fits spline surfaces to dense triangle mesh scan data. it's a complex process with pretty expensive tools like Geomagic Wrap for example. It's also possible to approach it with a polygon modeling toolset where it's called "retopology". There are retopo tools in many polygon mesh editing programs again like 3D Coat.

MoI is just not the right tool to work directly on the kind of data you have there.

- Michael